Measuring and recording atmospheric electrostatic potential

Various means have been available for many years to measure electrostatic potentials with ever increasing sensitivity and with decreasing current requirements. Instruments such as the electroscope or the common laboratory electrostatic voltmeter have been developed to the point where they operate reliably, with an input resistance of the order of 1016 ohms and higher, but in general these extremely sensitive instruments cannot conveniently be used to record potential over a period of time, thus requiring the continuous presence of an operator. A type of electrostatic voltmeter is described which is designed to record potentials as low as 1 volt d-c with an input resistance of 1014 ohms using an electrostatic generator to provide an a-c signal proportional to voltage, and a simple audio amplifier requiring only a commercial 1-milliampere recording meter in the way of auxiliary equipment.